Control system



SePt- 9, 1941- P. s. DICKEY 2,255,612

CONTROL SYSTEM Filed July 14, 193e 4 sheets-sheet 1 Sip/venne Flo. 1

Msn-

FIG.

PUMP Pfc/@canna INVENTOR P41/L 6. D/c/Ey Sept. 9, 1941. P. s. DlcKEY CONTROL SYSTEM Filed July 14, 195e 4 Sheets-Sheet 2 @SQ Q INVENTOR /QIUL 6. D/c/Ev' f ATTORN Sept. 9, 1941. P, s. DlcKEY CONTROL SYSTEM Filed July 14, 195e 4 Sheets-Sheet 3 lNvENTKoR PAUL. S. D/c/Er ISept. 9, 1941. P. s. DICKEYf cNTRoL SYSTEM Filed July 14, 1936 4 Sheets-Sheet 4 INVENTOR P4 aL 'D/c/D/ BY ATTOR Y after set forth. 'I'he Patented Sept. 9, 1941 CONTROL SYSTEM Paul S. Dickey, Cleveland, Ohio, assignor to'Bailey Meter Company,l a corporation of Delaware Applieaiien July 14, 193s, serial No. 90,615

32 Claims.

'I'his invention relates to' methods of and apparatus for operating vapor generators; particularly vapor generators of the drumless, forced ilow type, having a fluid ow path including'one or more long small-bore tubes, in .which the ilow. in the path is initiated by the entrance of liquid under pressure at one end, and the exit of vapor only at the other end; characterized by an inflow i of liquid normally greater than the outflow of vapor, the difference being diverted from the path intermediate the ends thereof.

Such a vapor generator, having ,-smallliquid storage and operated with wide range combustion devicesl forms a combination rendering practical extremely high heat release rates with the consequent ability to economically handle practically instantaneous load changes from minimum to maximum, and vice versa, without heavy standby expense, and is particularly suitable for operating conditions such as locomotive service. where load variations are of a wide range and are required to be lmet substantially instantaneously.

The generator has a minimum liquid storage capacity with 4a ,maximum heat absorbing surface so disposed and arranged as to be substantially instantaneously responsive to rapid changes .and wide diversities in heat release rate in. the furnace. The heat absorbing surface is arranged in relation to the path of the products of combustion and radiant heating so that the entering liquid is received at; the cooler end of the path.

y Further, the vapor generator insofar as the passage of combustion gases is conce i ed has a continuously increasing resistance to gas flow throughout the length of the p The heat absorbing surface, or flow path for the working medium, is preferbly comprised -of carried through the tubes of the generating section for the purpose of etness and preventing scale deposit, is diverte out of the separator under regulated conditions, as will be hereinolids carrying liquid dverted out of the flow,A path at the separator location is divided, with a portion sent to waste and the remainder` recirculated through the generating vportion of t' e Yiluid iiow path. It is in the control of sucly/hdlverted liquid and the recirculation thereof lthat I am particularly concerned in the present invention.

separator to dividey -Through the utilization of the present invention I am lenabled to recirculate a considerable percentage of the liquid entering the ilow, path and with advantageous results. For example, such recirculation may comprise twenty, thirty or even fty percent-of the'liquid entering the ilow path under pressure. -So long as such recirculation can be accomplished without loss of heat and `without the, 'expenditure of considerable power there are material advantagesto be gained.

In the forced circulation type of vapor generator comprising a once through fluid path of' one or more long, small-bore tubes, with a very small liquid ,storage and a very high rate of evaporation it is known that the vaporlzatioii zone within the path is the location where' substantially all of the solids carried by the liquid will be deposited or left in suspension through vaporization ofiiquid. 1f not deposited, due tothe extreme agitation of the liquid, they will serve to continuously increase the concentration of solids -in the liquid remaining in the tube path ahead cess of liquid iniiow tothe path o ver vapor outow from the path, the economizenand gener-A ating section prior to the separator willbe at all times wetted to prevent scale formation and will be provided with sufllcient liquid to wash al1 of the solids into the separator. Thus the separator comprises a relatively quiescent zone where separation of vapor and liquid may occur f 'as possible to save this loss. lPreierable operation would be to have a materially greater excess of expenditure and upkeep of such` heat exchanger apparatus is almost prohibitive. The recirculation of the liquid from the separator drum, regardless of the heat saving or loss of such liquid, means that the solids which have purposely been carried through into the separator for the purpose of taking them out of the tube path are now again brought into the tube path through recirculation.

pump 'or recirculate the liquid from the separator drum and with the knowledge that such a plurality of injectors will tend to be self-equalizing insofar as the combined eifect of heat and flow 5 distribution between the different tube sections is concerned. Any generating tube which has' the tendency, due to unequal application of heat for example, to generate more steam than its parallel tubes tends to become overheated through theV such e. vapor generator has substantially no 10 presence 0f generated steam within the tubes heat storage capacity either in the metal parts or in 'the small volume of liquid stored. It is capable, however, of very fast changes in heat release and absorption rates. However, through the advantages o f my invention I have been able l5 iZe 110W in the parallel tube Circuits. the Suben-- tution of an injector for each flow restrictor, v

to materially increase the speed at which load changes may be made, through the utilization of the liquid stored in the' separator drum atsubstantially vaporization temperature. Furthermore, I accomplish a recirculation of a very large tends tOWald im eqllliztOn '0f heat. tempelpercentage of the liquid inflow at substantially vaporizing temperature and without an increase in feed pump capacity or power requirements, and in fact under certain conditions of design I have been able tomaterially reduce the feed decrease in 110W 01' increase in heat input '(35 g by localized heating), the pressure drop in that pump size, or power requirement. I

In addition, the invention4 accomplishes the l very necessaryl desideratuni of balancing the plurality of parallel circuits insofar as resistance,

rather than a wetting liquids- While the previous flow restrictors or balancing resistors tend to minimize the effect of inequalities in tube resistance and thereby to equalwitha nozzle resistance commensurate with that of a restrictor, serves not only to retain the advantage of now equalization but additionally ture and proportions of the vapor-liquid mixture leaving the tubes. j Y f By way of example;vv should anyl particular circuit tend,l to become overheated due either to circuit increases due to the increased portion occupied by steam, and this of course may progress untilV excessive superheating is obtained at the 110W, temperature, and heat are comm-ned, 30 circuit outlet. However, the increased pressure Through the recirculation' of a very large percentage of the liquid inflow the concentrates are diluted and only a small percentage of the-spill-A over from the separator drum is sent to waste.

drop of the circuit raises the delivery pressure of the injector and thus decreases its pumping capacity and the amount of recirculated vwater from the separator drum which entersthe cir- .'In short, I desirably recirculate a higher per- 35 cuit. Therefore, the temperature 0f the mixed centage of liquid inasmuch as no heat is -lost and send to waste only a small percentagefto blow down the concentrates. I introducethe recirculated liquid into the flow path entrance through feedwater' and recirculated water entering this particular circuit is reduced and .likewise the 'f tendency toward excessively high ratio of 4steam to water, or high dry steam temperatures -leavthe agencyog injectors with approximately the 40 ing the circuit is checked. similarly, if a persame pressure drops as the previously used balancing,xv ow resistors, to serve as circulating pumps to increase the rate of circulation in the vaporization zone without requiring the pumping ticular circuit receives insufhcient heat, a smaller proportion of that :circuit will be occupied by steam andeth'e circuit resistance reduced. This results ,in a decrease in'injector delivery pressure of extra water by the main feed pumpV nor the lldthlls 811 increase in the amount 0f recirculoss of high potential heat occasioned by means of the spillover which formerly must go to the' feed watervheaters -or some similar point of low lated water pumped by the injector and entering that circuit.` The water withdrawn lfrom the separator 'drum for recirculating through the heat potential. With a larger percentage of in- ,Senertin lwl'iiienl 0f the flew Path iS'Preferbly flow being rcirculated instead of to drain, the '5 i'intreduced at theentrance tothesenerating p0ror equalizers between theeconomizer and vapor generating sections of the path, to attempt to attain equalization of ow through the tubes of the generating section and prevent overheating vof one. tube as compared to another through starvation of liquid. 'I'he flow restrictors are 6,0.

usually sections of tubing of relatively small di ameter introducing a 'resistance to flow of several times that of the tube path following, sorthat variations in flow resistance of said following tube path will bev cfmlnlmizcd effect relative tc the total resistance including the flow restriction- Through' multiplying the now resistance several timesin this manner-it is, of course,

to overcome such `resistance withv feed'pump '7o power. n l I propose to replace such flow restrlctors by injectors inserted in the several tube portions' of the ath at the entrance to the vapor generating v l sectilon. utilizing pressure drop therethrough to the amount of steam being generated in tion where the temperature of the water coming Fig. 6.)' Thus since the nettemperature of the,

-water entering the furnace or steam generating portionof the path depends on the'rat'io of re-v circulated to feed water, 'it is increased and the rate of steaming is accelerated. l l Nosuch heat and/orA temperature equalizing tendency is obtained with flow restrictors. When they aloneused, one mustdependupon the and temperature, since I have not lost the action'` of highpreasure drop in equalization of ows and at the same time I have gained a tendency toward equalization of fluid thermal conditions leaving the circuits by automatically regulatingv the'feed tcmpcrauircentering the circuits in an opposite content of. the liquid within the ilow path and any particular circuit. Thus the use of the injectors in place of the balancing resistors tends to automatically balance the tubes in the parallel circuit insofar as flow, heat, temperature, etc. ar

concerned.

The scheme consists essentially of elimination of the present balancing resistors or flow equalizers and the substitution therefor of injectors with approximately the same pressure drop which will serve as circulating pumps for the individual tube circuits to increase the rate of circulation in the vaporizing zone without requiring-the pumping of extra w'ater by the main feed pump.l The pressure drop of the present balancing resistors may be used as energy through the injector yaction to pump at least twenty to thirty percent of the-ilow rate back from the separator drum to the entrance of the vaporizing section.

It does not appear necessary to go into the' reasons for employing a plurality of long small bore tubes for the forced ilow path, inasmuch as this is well recognized in the art. Suilice it to say that having such construction it is of prime im'- portance that the plurality of circuits be equalized insofar as iiow, heat, temperature, etc. are concerned. x

In the drawings:

Figs. 1, 2, lZl'and 4 are diagrams of vapor the danger of damaged tubes therefrom.

In Fig. 3 3.5 units'of make-up are pumped, .5 unit is continually thrown to waste', and 1.5 units are recirculated from the entrance of the generating section. `In this example a small portion of liquid is continually thrown to waste with consequent loss of the heat therein and loss of the. power necessary to pump the liquid through the ow path. Furthermore, al second pump P is required 'for the recirculated liquid which is introduced after the economizer section. The total pump capacity is thus greater than in the examples Figs. 1 and 2. The advantage gained by the arrangement of Fig. 3 is a larger volume of liquid passing through the generating section,

thus diluting the concentration and furnishing units, a discharge to waste of .25 unit and a rei circulation of 1.75 units. Through the ,utilization of injectors between the economizer and generating portions of the'path I have m'ade use of thereof, and such apparatus shown in partially diagrammatic fashion.

To more readily bring out the salient features of my invention I have illustrated in Figs. 1, 2,

-in the work which the inflow pump must do.

lThe heat exchangers, employed for, the purpose the otherwise wasteful pressure loss of the flow equalizers. plurality of circuits would have substantially the same pressure drop as the previously mentioned flow equalizers but would utilize such pressure drops in actually pumping into the generating section the recirculated spillover. Thus the pump of Fig. 3 indicated at P would be eliminated and the make-up pump would be of substantially the same size as required in Fig. 3. There is substantially no loss in heat in the large volume of recirculated'spillover. This recirculated liquid at nearly vaporizing temperature is available at the inlet to the generating section at all times, and as previously brought out is fed proportionate to the rate of operatlon of the generator as a whole. In'other words, as demand upon the generator increases, the injector action will auof conserving the heat of the waste liquid, are

expensive insofar as capital investment, repair, upkeep, etc. are` concerned. Twenty-iive percent of the total water pumped by the inflow pump is thrown to waste and a certain amount of l are continually gaining in concentration of solids.

The pump is of the same size as in Fig. 1 and while the heat exchangers are not necessary and the heat of the spillover liquid is conserved,it is at the expense of rapidly increasing the solids tomatically increase, thus drawing a greater volume of recirculated spillover from the separator drum, utilizing the stored liquid thereon/and at no additional pumping expense. .The additional volume of highly heated liquid entering the genl erating section will materially speed up the loadtaking-on ability of the generator as al Whole.

This is further amplied due to the swell of the liquid within the separator when load suddenly increases and pressure on the separator correspondingly ,suddenly decreases. Such swell or increased Volurne of liquid within the separator will afford a very welcome additional supply of highly heated liquid to the entrance of the generating section'.

generating section will be automatic at times of change in loa-d and self-equalizing to counteract In other words the injectors of the i may be provided.

adverse effects of localized heating or other sources of trouble in operation. Such equalizations will'be of ilow, temperature, heat, etc.

Having now described in a more general manner the advantages of my invention in relation to known constructions and methods of operation, I will now describe in detail the apparatus utilized in carrying out the preferred form of the invention.,

The drumless forced flow vapor generator to which "the present invention is directed is diaface arranged as contained within the enclosure represented by the dot and dash lines. V

'Ihe iiow path for the workingmedium is com- The generator includes an placement pump which hot well. i

'Ifhe liquid from the economizer outlet header 2 is conveyed by a tube 3'to a manifold tube I may be connected to Aa 'from which the liquid is distributed to the generating section through, in this instance, ilve ingaminatically illustrated in Fig. 5 to indicate gas 1 ilow,"working iluid flow, and heat absorbing surprised of long small-bore tubes brought together at suitable headers. j conomizer I at the cooler end of the gas passage u and which receives liquid from a positive dis-- jectors 5, each of which has a certain resistance drop'preferably greater than the particular id now passage which it serves, and whereby the liquid is proportionately distributed to each of the tubular fluid-now passages 5, 1, 3. 3 and I3 constituting the generating section oi.' the assemwhich comprises door, wall, screen and roof Vportions as indicated.

A an oil burner Il supplied by agpipe I5 and an'air chamber I5 supplied by acon'duit Il. Ordinary provision for initial ignition, safety features,. etc.

economizer and may contact a turbine 2| drives the nquid reed Y associa passes to and through the superheater I2 to a main turbine 2|! illustrative of a. vapor consuming device. Products o! combustion pass successively through the generating section, superheater, and part or all of the separator. l

An auxiliary pump I9, the air blower 22, and the fuel supply pump 23. While I have illustrated these devices diagrammatically andl as though all are located to be driven by the same shaft and at the same speed, it will be understood that the necessary gear reduction or driving connectionsbetween the several 'devices are known and wouldrbe properly designed as to relative speed, power, etc.4 andv that I merely intend to indicate. that the auxiliary turbine 2l drives the devices i9, 2 2 and 23 simultaneouslyand in unison. e

'Ihe rate of supply of fuel oil to the burner I 3 is primarily controlled by the speedrof the oil pump 23 but the supply of oil is further regulated by AAthe throttling of a regulating valve 23 locatedin the pipe I5, and the rate of ilow is continuously measured by a meter 25.

The rate of supply of .air to support combustion is primarily determined by the speed of the blower 22, but is further under the control of a' damper 25 positioned in the conduit Il at the inlet to the blower. The rate of supply of air is continuously measured by a flow meter 21.

The rate of VSupply or liquid under lpressure*V through the conduit I3 is primarily controlled by the speed of the pinnp I9 but is further influenced 4through the positioning of a regulating valve 23 at the suction side of the pump.

ed across the vertical elevation of the sepltor. A'float is adapted to rise and fall with the surface of the mercury in one leg and to thus cause a positioning of a pointer 33 relative to an index 3| to'advse the instantaneous value'of liquid level and to further vertically vposition the stem ru rig; s the epmoveripipelr is divided to 'form a controlled bleed to waste; a controlled iiow to the injectors, and a fixed ilow to the injectors.

. In Fig. 6 v1 illustrate diagrammatically -the -ilow path of the working medium without' respect Vto the'sequence oiheating. I have indicated certain temperature-1)rassure'conditions aa` a l singlee'xampleof what might be encountered under certainfccnditionsof design and operation-ll dierent .forms of injectors which may be uti-L l lized in the individual'ilow circuits between the economizeri'and theV vapori'zing or generating zone. The particular injector forms no' part of the present invention but will bie-designed to give t 32 of .a pilot valve 33 to establish'a'n Vaix' loading' pressure representative of liquid'leveh Such-an` tive of rate ofvapor o utiiow is eil'ective within a chamber ofthe averaging relay 35. The averaging relay` 35 is connectedV by means of a pipe 'u with vthe diaphragm chamber of the valve 2s Y to position the same responsive to both variations in rate of 'vapor outflow and variations in liquid level within the separator II.l For examp1e,.1iquid iniiowis held roughly in' proportion desired pressure drops, tlow capacities and char- Referring'- now in particular to-Fig. 10 I illus- `tratezthe fluid iloW path as a single sinuous tube, to' the econcmizer section I- of which liquid is supplied under pressure through a pipe I3 from a pumpV I5, which while it is 'illustrated in Fig. 5 as a positive displacement pump may be of any .suitable type 'and which I-have therefore illustrated in Fig. l0 merely diagrammatically. From 1 ,the economizerv section the viiuid passes to and through the generating section discharging into to vapor outiiow and is readdusted to maintain desirable level within the separator. rate of liquid iniiow isnot entirely under the control of regulating valve 23, it is ,primarily so for the pressure drop across the valve 23 isutilished representative of vapor outilow pressure effective in positioning the damper 23 as well as v Whilefthe a diaphragm actuated valve 48 in one spillover` line from the separator'll.

'I'he rate of flow meters 25, 21 coact to position apilot stem 49, establishing a loading pressure eil'ective for positioning the fuel oil valve 24. Should fuel flow-air flow depart from desired relationship the valve 24 will be positioned to re#- adjust the iiow of fuel oil and reestablish such desired relationship.

Certain features of the general arrangement in method and vapparatus for operating such a vapor generator are disclosed and claimed in my copending application, Serial No.- 55,023, iiled in the United States Patent Oiiice December 18, 1935, now Patent 2,170,346.

The concentration of solids in the liquid with? A second pipe 52 leads from the separator 4II to waste or any desired location. Flow through the pipe 52 is under -the control of the valve 31 and the arrangement is s'uch that the valve 3'! is to be opened only under emergency high level conditions within the separator l I. Should level within the separator reach a predetermined high level the level responsive device 29 will so position the pilot stem 32 that an air loading pressure will be established' through the pipe 36 upon the Valve 3l and cause the valve to open quickly and in large degree to take care of such emer gency conditions until the level is brought down to below the emergency point.

A third pipe 53 leads from the separator H and is branched as at 54. In the pipe 53 is located the regulating valve 48 under the control of a loading pressure established representative of vapor outflow pressure. 'Ihe branch 54 has a fixed resistance 55 and joins the pipe 53 again before the pipe 53 reaches the injectors 56. It

cent ofthe vapor outilow rate as liquid is allowed to pass through the resistance 55 and enter the injectors 55 to prevent superheating in the generating section and to balance steam quality of mixture from the various circuits entering the valve 45 inthe branch 53 is opened responsive to an indication of load as. represented by vapor outow pressure and this serves to reduce the separator liquid level and increase the ilow through-the circuit in the generating section up to 1.70 to 2.0 times the output rate, thus utilizing the swell in the separator drum to make additional vapor output. Thus by materially reducing the total resistance of thelspillo'ver lines 53,

" 54 as much as seventy to eighty percent of ilow can be recirculated through the spillover lines at timesof sudden load increase when there is a surge of level within the separator drum.

Under emergency conditions should the level within the separator Il rise to a, dangerous point,

the valve 31/will be opened quickly and in considerable degree to relieve the condition. A very small amount of liquid is continually passed to waste through the valve 5| under the control 4of a concentration or conductivity cell 50. v

While I have chosen to illustrate and describe certain embodiments of my invention I am not to be limited thereto but only as to the claims in view of prior art.

What I claim as new, and desire to secure by Letters Patent of the United States, is:

l. The method of operating a vapor generator of the forced flow type having a separator be-- tween the generating and superheating portions of the ow path, which includes recirculating a material percentage of the liquid leaving the generating section, and varying the percentage is understood that the pipe 53 will be branched to each of the injectors 55 located in the individual parallel tube circuits as indicated in Fig. 5.

Under normal. conditions of operation variations in vapor outflow eiective upon the meter v38 will result in. variations of auxiliary turbine speed to proportion liquid inilow, air and oil to the variations in load. Should level within the separator vary. such changes willalso be eiective in controlling auxiliary turbine speed, al-

though the magnitude of the changes in auxiliary turbine speed for changes in level may be quite different than the magnitude of changes in auxiliary turbine speed for changes-in vapor outflow rate.

The supply of air to support combustion is re- Fuel oil supply is readjusted-in accordance with fuel iiow-air flow relation. 1

As indicated in Fig. 4 and previously described,

va considerableportion of the liquid entering the separator Il is recirculated to the entrance of the generating section and this may amount to ltwenty, thirty orfeven ilfty percent `by weight.

During norma! operation twenty to thirty perrecirculated responsive to load on the generator.

2. The method of operating a vapor generator of the forced flow type having a separator between the generating and superheating portions of the flowv path,- which includes, recirculating a ma'- terial percentage of the liquid entering the'separator,'and utilizing thfepressure drop of a portion ofthe path to introduce the recirculated liquid at the entrance of the generating section.

3. The method of operating a vapor generator of the forced flow type having a separator between the generating and superheating portions of the iiow path, which includes, passing iluid under pressure through a plurality of parallel circuits in the generating portion, recirculating a material percentage of the liquid entering the generating circuits through said circuits, and

' utilizing injector action at the entrance to the individual circuits to proportion the circulation to the circuits.

4. The method of operating a vapor generator of :the 4forced flow type having a plurality of parallel circuits in the generating portion, which includes, diverting a material percentage of the liquid from adjacent the vaporization zone of the path,- reintroducing the diverted liquid to the plurality of generating circuits, continuously passing a portion of the diverted liquid, and -regulating the flow of the remainder responsive to loa on the generator. v

5. The method of operating a vapor generator. of the forced flow type having a plurality of parallel circuits in the generating portion, which includes, diverting a material percentage of the `liquid from adjacent the vaporization zoneof the path, reintroduclng the diverted liquid to the generating circuits, allowing a portion ofthe diseparaton Upon increasing load the regulating n Iliquid from adjacent lverted liquidto continuously `pass to the circuits, Y

jacent the vaporization none, an injector in each' generating circuits, verted liquid to continuously pass to the circuits,

of said tube circuits, and means diverting liquid from said separator to the injectors.-

"1. In combination, avapor generator ot the' forced flow type having a plurality of tube circuits inthe generating portion, an injector at the entrance of each of-said circuits, and means diverting liquid from adjacent the vaporization zone of the ilow path and returning such liquid to the plurality of injectors.`

8. The method f Operating a vapor generator of the forced flow type having a ,generating portion. which includes, .diverting a material percentage of the liquid from adjacent the vaporization zone of the path, reintroducing the di- 'verted liquid to the generating portion, continua portion of the. diverted liquid. and regulating the'iiow of the remainder responsive to loald on the generator.

i 9. The method of operating a vapor generator snowing s portion of themand regulating the flow of .the'remainder` of diverted liquid responsive to .a variable condition in the operaticn of the vapor generator.

l5. The method of operating a vapor generator y of the forced flow type' having a generating por'- tion, which includes, diverting a material percentage of the liquid from adjacent the vaporization zone of the path, reintroducing the diverted liquid to the generating portion, continuously a portion of the-diverted liquid, and regulating the flow of the remainder responsive to a variable condition inthe operation of the vapor generator.

16. The method of operatingavapor generator "having a small liquidstorage with ahigh rate of e evaporation, which includes, continuously divertof the forced ilow type having a generating portion, which includes, diverting a, materialpercentage of the liquid from adjacent the vaporiza tion zone of the path, reintroducing the diverted liquid to the generating portion, allowing a portion o f the diverted liquid to continuously 'pass to the generating section, and controlling the flow of the remainder of diverted liquid responsive to vapor outflow pressure.

10. The method of operating a vapor generator of the vforced flow type having 'a separator between the-generating and superheating Vportions of the flow path, which includesrecirculating a material percentage of the liquid leaving the vgenerating section,Y and varying the percentage recirculated responsive to vapor outflow presure.

l 11. The method of operating a fluid treating system wherein a portion of the entering liquid is .vaporized, which includes, passing the liquid and vapor mixture to a relatively quiescent separator section, allowing the' vapors to separate and pass away, a portion of the unvaporized nuidto the 4entrance of the treating zone, and varying the percentage recirculated responsive to a vapor output variable.

l2. The method'cf operating a iluid treating system 'wherein a portion of the `entering liquid is vaporized, which includes, passing the liquid and vapor mixtureto a relatively quiescent separator section, allowing the vapors 'toy separate and pass away, recirculating a 'portion of the unvaporized fluid tothe entrance of the treatin sone,l and varying the percentage recirculated responsive to vapor outflow pressure.

f 13. The method of 'operating a vapor generator Y of the forced flow type having a separator between the generating and'superheating portions of the uuid now path, which includes continuous-V includes. diverting a material percentage of the the vaporization sone of the litt-h. reintrodiicing y system wherein a portion of the entering liquid portion of the path to introduce recirculatedliqing a material percentage of the liquid fed -to the generator .from adjacent the vaporizatlon zone of the generator, reintroducing such diverted liquid to the generator at another location, and controlling the percentage reintroduced responsive to a variable condition in the operation of the vapor generator. Y

17. The method of operating a vapor generator having a forced flow path receiving liquid imder pressure Iat one end and delivering vapor at the other and having heating provisions, which includes, continuously diverting a material percentage of the liquid from adjacent the vaporization zone of thepath, reintroducing at least a portion of the diverted liquidto thepathlat another zone, and regulating the percentage reintroduced responsive to a variable in the op- 'eration of the vapor generator.

18. The method of operating fluid is vaporized, which includes, :passing the liquid andV vapor mixture to a relative quiescent separator section, allowing the vapors to separate Vand pass away, continuously recirculating aportion of the unevaporated fluid to the entrance of the treating zone, and .varyingthepercentage rethe fluid.

. 19. The method of operating a v apor generator of theforced now type having a separator bei tween the generating and superheating portions i of the flow path, which includes, lrecirculating a material percentage of the liquid entering` the separator, and utilizing the pressure drop of a.

uid at said portion of the path.

20. .In combination, a vapor generator ofthe and returning such liquid' to the 'plurali-.y of injectors, and means responsive to a variable condition of the iiuid and adapted to regulate the Y- oftheforcedfiovrtypehavingapluralityofv .parallel circuits in the generating portion, which un diver-sea' uqula te the 1s the path. Y

22. In combination, a vapor generator ofthe Aiii. In combination. a vapor lgenerator ofthe forced now type having a plurality of parallel tube circuits in the generating portion of the fluid ow path, means continuously recirculating liquid from adjacent the vaporizatlon z one of thepath to a location near the of the .generating portion, and other means under the control of a vapor outflow variable supplementing such recirculated liquid with liquid from forced i'iow type having'a plurality of parallel tube circuits in the generating portion ofthe iiuid flow path, a separator in the path adjacent the vaporization zone, means continuously recirculating liquid from said separator to the generating portion responsive to a variable of the fluid, means diverting liquid from the separator responsive to a measure of concentration of the liquid, and means diverting liquid from the separator when an excessive level of liquid Within the separator is reached.

23. The method of operating a vapor generator of the forced iiow type having a plurality of parallel ,circuits in the generating portion, which includes, diverting a material percentage only of the unevaporated liquid from adjacent the vaporization zone of the path, reintroducing the diverted liquid to the plurality of generating circuits, and automatically proportioning the recirculated liquid to the generating circuits.

24. In combination, a vapor generator of the forced flow type having a plurality of tube circuits in the generating portion, an injector at the entrance of `each of said circuits, and meansdiverting fluid from adjacent the vaporization zone of the flow path and returning such fluid to the plurality of injectors. i

25. The method. of operating .a forced circu lation fluid treating system wherein the entering fluid contains a material percentage of liquid, which includes, heating the treating zone of 'the forced circulation path to a degree whereby a portion of the entering liquid is vaporized, passing the liquid and'gas and vapor mixture to a relatively quiescent separator section, continuously recirculating a portion of the treated uid to the entrance of the treating zone, and varying the percentage recirculated responsive 1:01a variable condition of the fluid.

26. The method of operating a uid treating system wherein a portion of the entering fluid is vaporized, which includes, passing the liquid and vapor mixture to a relatively quiescent separator section, allowing the vapors to separate and pass "away, supplying. liquid to the system in excess -rator to eifect the introduction of recirculated v 27. In combination, a vapor generator of the 4 forced iiow type having a generating tube portion, a separator adjacent the vaporization zone, a pipe connecting the separator with the entranceof the generating tube portion providing a substantially vilxed resistance non-regulable iluid path through which liquid returns from the separator 28. In combination, a/vapor generator of the forced iiow type having a'generating tube portion, a separator adjacent the vaporization zone, a pipe connecting the separator with the entrance of the generating tube portion providing a substantially iixed resistance non-regulable uid path through which liquid returns from the separator to the entrance of the generating tube portion, a second'pipe parallel to said rst pipe 'and having therein a regulating valve, and means positioning .which liquid returns from the separator to the entrance of the generating tube portion, a second pipe parallel to said first pipe and having therein a regulating valve, and means responsive to a variable condition of the iluid positioning said regulating valve.

30. The method of operating a vapor generator of the forced ow type having `a separator between the generating and superheating portions of the flow path, which includes, recirculating a material percentage only of the liquid entering the separator, and utilizing the fluid velocity through 'a portion of the path prior to the separator to eilect the introduction of recirculated liquid at said portion of the path.

3l. The method of operating a fluid treating systemwherein a portion 'of the entering liquid is vaporized, which includes, passing the liquid and vapor mixture to a relatively quiescent separator section, allowing the vapors to separate and pass away, recirculating a portion only of the unevaporated iluid to the entrance of the treating zone, and utilizing the iluid velocity through a portion of the path priorto the sepaliquid at said portion of the path.

32..In combination, a vapor generator of the forced iiow type having a generating tube portion, a separatoradjacent the vaporization zone,

'a pipe connecting the separator with the entrance of the generating tube portion providing a path through which a portion only of the unevaporated liquid returns from the separator to the entrance of the generating tube portion, an injector type means in the path near the entrance of the generating portion and to which said pipe connects whereby the velocity e'ect of the fluid p through the injector causes'the recircuiatedI fluid a to enter the path, and means for varying the percantare of the uuid recircuiateo.

Paonanrcnr. 

